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Explore Scientific 127 eye pieces

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#1 GunArm

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Posted 20 July 2019 - 11:18 PM

After about 18 months of research and waiting to see if the interest would fade, I've decided to take the plunge!

 

I've decided on an ES 127mm APO with the new FCD100 glass.  I've chosen primarily for it's potential for astrophotography, but I want to build my skills and spend my money in stages, starting with getting it up and running visually.  Hoping for some experienced sanity checks.

 

ES FCD100 127mm

focal length 952mm

f ratio 7.5

2.5" focuser

 

I admit I've skimped on my research of eyepieces until the week or so of putting together a purchase plan, but I think I have a pretty good idea what I'm after.  I've already got a handful of cheap eyepieces I used on a borrowed dob, but I want to invest in two good eyepieces of approximate optical quality as the APO to not be bottlenecks. 

I think I am initially going to avoid high magnification EPs so that I will be safely far from the highest useful magnification, will have less issues with the atmosphere, and will err on the side of brighter crisper images in a large apparent field of view.

I am buying the scope direct from ES and I think I'm going to get the EPs from them for native compatibility and similar quality to the telescope.  I like the look of their EPs anyway and without having one in my hand they seem to have good build quality.  So, my current plan is to get a 34mm in their 82degree series, and a 24mm in the 68degree series, and also to buy their 2x focal extender to also get 12mm and 17mm viewing options.  So effectively I'd have 34mm, 24mm, 17mm and 12mm.  AKA 28x, 40x, 56x, and 80x.

I may or may not also just go for a third EP, maybe their 14mm (which costs half as much as the other two), that I could get 136x out of with the barlow just to play with viewing near the seeing limit.

 

So my questions are:

Does this seem reasonable?

I've heard some (but not all?) focal extenders also double eye-relief.  Will the ES focal extender with these eyepieces result in too much eye relief?

What is the problem with going below the lowest useful magnification of a telescope?  Is it that you can't even see an image, or the image distorted, or you just don't get the telescopes full potential light gathering into your pupil?

Would I be able to use this scope and these eyepieces with any kind focal reducer?  I think the answer is no, I know reducers on 2" EPs are uncommon, I think Celestron has one at .63 don't know much about it, but I read that many optical setups have trouble focusing like that.

 

Comments appreciated!



#2 SeattleScott

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Posted 21 July 2019 - 09:03 AM

There is no such thing as a 34mm 82 degrees eyepiece . ES has a 34mm 68 or a 30mm 82.

Either one would be a great choice, just realize that the 30/82 is big and heavy. Let’s say you get the 34/68. Cheaper, lighter, better exit pupil for using nebula filter. The 24/68 is too close. Medium power with a scope like this would be like a 9mm. High power 3.5-5mm. With the focal extender you could get 34 and 17 out of one eyepiece. Then get the 8.8 82 degrees, which can barlow to 4.4. Now you have minimum power, max FOV for finding things, low/medium power at 17mm for large open clusters, Orion Nebula and such, medium power at 8.8 for general DSO work and high power at 4.4 for lunar/planetary.

Scott

#3 Auburn80

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Posted 21 July 2019 - 09:38 AM

Barlows/multipliers are an excellent way to expand your eyepiece collection and get good eye relief at higher powers.
Here's the rub though IMHO. You'll be stacking a 1.5 lbs eyepiece onto a 1 - 1.5 lbs multiplier into a 2" diagonal. Makes for a tall & heavy arrangement. What I did was to have a single 2" low power eyepiece then swapped to 1.25 for shorter fls and used a 1.25" multiplier for those.
If you decide to go with a 2" Barlow then Scott's suggestions are spot on.

#4 GunArm

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Posted 21 July 2019 - 08:11 PM

Appreciate the responses, unfortunately I was not able to make use of them since I had a significant coupon with ES that expired early this morning, and I went ahead and bought the barlow, the 34, 24, and 14 last night.  Still, the responses are interesting.

 

There is no such thing as a 34mm 82 degrees eyepiece . ES has a 34mm 68 or a 30mm 82.   Either one would be a great choice, just realize that the 30/82 is big and heavy.

My mistake, I got the two numbers mixed.  The 30/82 was sold out so I was looking at 34/68 and 24/82 and 14/82.

 

Let’s say you get the 34/68. Cheaper, lighter, better exit pupil for using nebula filter. The 24/68 is too close. Medium power with a scope like this would be like a 9mm. High power 3.5-5mm. With the focal extender you could get 34 and 17 out of one eyepiece. Then get the 8.8 82 degrees, which can barlow to 4.4. Now you have minimum power, max FOV for finding things, low/medium power at 17mm for large open clusters, Orion Nebula and such, medium power at 8.8 for general DSO work and high power at 4.4 for lunar/planetary.

Scott

Glad you made me aware 9mm is middle power on this scope, sounds like I'm pretty bottom-heavy with 34 24 17 14 12 and 7.  That's kindof a bummer but I'm not too broken up about it.  I can always add one more to get the high end.  Actually I've got a cheaper 9mm plossl laying around I can play with in the mean time.  I just didn't want to spend money (immediately) on high magnification that hits the scope optics/seeing limit, or is frustratingly dark.  Once I get these I should get some hands on experience to steer my future pickings.  If the 34 and 24 are too close I might trade the one I like less for something on the shorter end.

 

 

Barlows/multipliers are an excellent way to expand your eyepiece collection and get good eye relief at higher powers.
Here's the rub though IMHO. You'll be stacking a 1.5 lbs eyepiece onto a 1 - 1.5 lbs multiplier into a 2" diagonal. Makes for a tall & heavy arrangement. What I did was to have a single 2" low power eyepiece then swapped to 1.25 for shorter fls and used a 1.25" multiplier for those.
If you decide to go with a 2" Barlow then Scott's suggestions are spot on.

I wasn't really too worried about weight, within reason, since my mount (EQ6-R) was chosen to support the weight of AP gear.  But you bring up an interesting question, what exactly is the benefit of 2" over 1.25", or the detriment vice versa?  I thought it was strange the that Stratus/Hyperion eyepieces choke down to 1.25.  I get that it's for compatibility, but is that a waste of a 2" optical train?



#5 Auburn80

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Posted 21 July 2019 - 09:16 PM

One can achieve greater fields of view in the 2" format than is possible with 1.25". Disadvantages are size/weight and expense.

#6 letimotif

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Posted 21 July 2019 - 09:52 PM

As someone who undertook a lot of research before making your purchasing decisions, I hope you are happy with all your new gear when it arrives.

 

Over the years I've bought and sold a number of eyepieces.  Currently, I've been quite satisfied with and use various ES eyepieces in their 82 and 100 degree line, as well as one 40mm 68 degree EP.

 

You did not mention Astromart, though. I wanted to make sure that you are aware of Astromart as it is a great place to seek out and find eyepieces that are practically new, and available at a steep discount from reliable sellers.

 

For example, Astromart currently has in its Eyepiece Classifieds a 30mm ES 82 degree eyepiece described as being in "pristine" condition for $240.  The seller is someone who has a five star (highest) rating from 426 other members.

 

If you know about Astromart, and are a member, great.  If not, do keep them in mind when you decide to expand your eyepiece collection.  And, let's not ignore Cloudynights' own Swap and Shop forums here.

 

Oh, by the way, I have no affiliation with the seller in the classified ad I mentioned, nor am I affiliated in any way with Astromart other than having a membership qualifying me to view classifieds and auctions.

 

Best of luck, and clear skies.


Edited by letimotif, 21 July 2019 - 09:53 PM.

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